Rather than writing multiple functions that take different types as args and return different types (say int8, int16, int32, etc.) but do the exact same thing, with generics, you can instead write one function that takes a number (which could be any int type) and return a number, and you only wrote one function. That is generics in a nutshell. The function is generic, not specific to one type.

Generics allow for less code, thus they are easier to debug, test and reason about. I've used them a lot in C++ and I do miss them in Go. It's not a deal breaker for me either way, but for people who write larger, more complex code, not having them makes it more difficult (more code to write, test and maintain).

C does not have generics either. Go is a lot like C in this regard.